Ensuring optimal treatment outcomes while minimizing adverse reactions has always been a central challenge in medical aesthetics. Traditional high-fluence laser protocols are effective but frequently associated with complications such as post-inflammatory hyperpigmentation (PIH) and barrier disruption—especially in melanin-rich Asian skin types.
Low-Fluence, High-Spot-Size (LFHSS) laser technology offers a safer alternative by combining gentle thermal effects với precise pigment targeting. Today, this technique is widely applied in 1064 nm / 755 nm, nanosecond Và picosecond platforms.
This article provides a comprehensive scientific and clinical overview of LFHSS: its origin, standardized definition, indication-specific parameters, treatment precautions, and contraindications—offering physicians a structured and evidence-based protocol.
1. Origin and Standard Definition
1.1 Historical Background
LFHSS can be traced back to the mid-2000s, when Korean dermatologists first applied large spot sizes and low fluence với Q-switched Nd:YAG 1064 nm nanosecond lasers for melasma management—coining the term Laser Toning.
The approach quickly gained global popularity and later inspired technologies such as “Whitening Toning,” “Carbon Peeling,” and other low-fluence programs.
With device evolution, LFHSS expanded to 755 nm nanosecond and picosecond lasers, enabling more precise pigment-selective treatment and significantly reduced risk of complications.
1.2 Standard Definition of LFHSS
LFHSS must meet all of the following technical criteria:
| tham số | Standard Requirement |
|---|---|
| Kích thước điểm | ≥ 6 mm |
| Fluence | ≤ 3 J/cm² |
| Treatment Endpoint | Mild warming or slight erythema |
Wavelength Characteristics
- 1064nm → deeper penetration; targets dermal pigment (melasma, Hori’s nevus, PIH)
- 755nm → higher melanin absorption; ideal for epidermal pigment (freckles, epidermal melasma)
Thời lượng xung
- Picosecond → photomechanical pigment fragmentation + skin rejuvenation
- Nanosecond → epidermal/dermal modulation and skin conditioning
2.1 Pigmentary Disorders
(1) Melasma – 1064 nm Nanosecond Laser as Standard of Care
Recommended Parameters
- Spot size: 6–8 mm
- Fluence: 1–3 J/cm²
- Frequency: 5–10 Hz
- Interval: every 2–4 weeks
- Total sessions: ≤ 15 sessions
(Exceeding 15 sessions increases risk of mottled hypopigmentation.)
Cơ chế:
LFHSS applies “subcellular selective photothermolysis”—breaking melanosomes while preserving melanocyte viability, thereby reducing PIH and rebound pigmentation.
(2) Hori’s Nevus / Dermal Melanocytosis
First choice:
755 nm picosecond laser
→ stronger photomechanical fragmentation
→ lower risk of PIH
If using a 1064 nm nanosecond device:
- Spot size: 6–8 mm
- Fluence: 1–3 J/cm²
- Frequency: 5–10 Hz
- Interval: 2 tuần4 tuần
2.2 Inflammatory & Degenerative Skin Conditions
(1) Rosacea & Steroid-Induced Dermatitis
Recommended (1064 nm nanosecond “toning mode”)
- Spot size: 6–8 mm
- Fluence: 0.3–1.5 J/cm²
- Interval: 4 tuần
Mechanisms:
- Modulates vascular reactivity
- Reduces inflammatory cytokines
- Accelerates barrier repair
- Improves flushing and sensitivity
(2) Skin Rejuvenation (755 nm Picosecond + MLA Technology)
Recommended Parameters
- Spot size: 6–8 mm
- Fluence: 0.5–1.0 J/cm²
- Frequency: 5–10 Hz
- Interval: every 4 weeks
Những lợi ích:
- Collagen neogenesis
- Texture and pore refinement
- Fine lines reduction
- Thời gian ngừng hoạt động tối thiểu
3. Treatment Precautions
3.1 Patch Test Protocol (Mandatory Step)
- Start with 1 J/cm², deliver 1–2 shots, observe for 5 minutes
- If purplish erythema or pain → decrease fluence by 0.2–0.5 J/cm²
- If minimal reaction → increase by 0.2–0.5 J/cm² (not exceeding 3 J/cm²)
- During full-face treatment, ensure the skin temperature stays below 40°C after 2–3 passes.
3.2 Preventing Excess Energy Accumulation
- Overlap rate: ≤ 10%
- Melasma: do not exceed 15 lifetime sessions
- quanh mắt & perioral areas: reduce fluence by 20%
- Always enable device cooling
(air cooling / contact cooling / cryogen depending on device)
4. Contraindications
4.1 High-Vascular-Density Lesions (Port-Wine Stain, Hemangioma)
1064/755 nm wavelengths have low hemoglobin absorption →
LFHSS fluence is insufficient to coagulate vessels →
May worsen vascular proliferation → Contraindicated
4.2 High-Density Tattoo Pigment
LFHSS fluence cannot reach the “instantaneous pigment explosion threshold” needed for tattoo removal.
- Leads to inadequate fragmentation
- Requires excessive sessions
- Increases inflammation and PIH
→ Use high-fluence Q-switched or picosecond protocols instead.
4.3 Hyperkeratotic Lesions (Seborrheic Keratosis, Warts)
LFHSS is không mài mòn and relies mainly on photobiomodulation →
Cannot vaporize keratin →
May stimulate further hyperkeratosis → Contraindicated
Phần kết luận
LFHSS technology, based on large spot size and low fluence, provides a safer, gentler laser strategy across multiple wavelengths and pulse modes. It offers significant benefits in:
- Pigmentary disorders
- Inflammatory skin conditions
- Trẻ hóa da
- Sensitive-skin management
However, clinicians should note:
- Clear clinical consensus currently exists only for melasma
- 15 sessions increases risk of mottled hypopigmentation
- Evidence for rosacea and rejuvenation requires more long-term RCTs
- Contraindications must be strictly followed
Future studies—especially multicenter randomized controlled trials—are essential to further define LFHSS treatment boundaries, optimize parameters, and elevate safety standards across medical aesthetic practice.
More related blogs
Tại sao Laser CO₂ Fractional giúp làm lành vết xăm
Q-switch và laser YAG cho chăm sóc da chuyên nghiệp là gì?
Q-Switched ND: YAG Laser cho các tổn thương sắc tố: Điều trị Nám
Làm thế nào hiệu quả là ND: YAG laser có hiệu quả để điều trị NELASMA?
Laser Pico Q-Switched: Hướng dẫn đầy đủ về cơ chế, phạm vi điều trị & Lưu ý an toàn
Laser Pico và Laser CO₂ – Cái nào tốt hơn cho việc xóa hình xăm?
Laser chuyển đổi Q: cơ chế, chỉ định, chống chỉ định, tham số & Các biện pháp phòng ngừa
Thời gian phục hồi bằng laser Q-Switch: Điều gì sẽ xảy ra và cách tăng tốc độ hồi phục
Portable Picoway picosecond Machine Operation
Máy laser tốt nhất để loại bỏ hình xăm chuyên nghiệp vào năm 2025 là gì?
